1. 8.5.x core/includes/form.inc
  2. 8.0.x core/includes/form.inc
  3. 8.1.x core/includes/form.inc
  4. 8.2.x core/includes/form.inc
  5. 8.3.x core/includes/form.inc
  6. 8.4.x core/includes/form.inc
  7. 8.6.x core/includes/form.inc
  8. 4.7.x includes/form.inc
  9. 5.x includes/form.inc
  10. 6.x includes/form.inc
  11. 7.x includes/form.inc

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includes/form.inc
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<?php

/**
 * @defgroup forms Form builder functions
 * @{
 * Functions that build an abstract representation of a HTML form.
 *
 * All modules should declare their form builder functions to be in this
 * group and each builder function should reference its validate and submit
 * functions using \@see. Conversely, validate and submit functions should
 * reference the form builder function using \@see. For examples, of this see
 * system_modules_uninstall() or user_pass(), the latter of which has the
 * following in its doxygen documentation:
 *
 * \@ingroup forms
 * \@see user_pass_validate().
 * \@see user_pass_submit().
 *
 * @} End of "defgroup forms".
 */

/**
 * @defgroup form_api Form generation
 * @{
 * Functions to enable the processing and display of HTML forms.
 *
 * Drupal uses these functions to achieve consistency in its form processing and
 * presentation, while simplifying code and reducing the amount of HTML that
 * must be explicitly generated by modules.
 *
 * The drupal_get_form() function handles retrieving, processing, and
 * displaying a rendered HTML form for modules automatically. For example:
 *
 * @code
 * // Display the user registration form.
 * $output = drupal_get_form('user_register');
 * @endcode
 *
 * Forms can also be built and submitted programmatically without any user input
 * using the drupal_execute() function.
 *
 * For information on the format of the structured arrays used to define forms,
 * and more detailed explanations of the Form API workflow, see the
 * @link forms_api_reference.html reference @endlink and the
 * @link http://drupal.org/node/204270 Form API guide. @endlink
 */

/**
 * Retrieves a form from a constructor function, or from the cache if
 * the form was built in a previous page-load. The form is then passed
 * on for processing, after and rendered for display if necessary.
 *
 * @param $form_id
 *   The unique string identifying the desired form. If a function
 *   with that name exists, it is called to build the form array.
 *   Modules that need to generate the same form (or very similar forms)
 *   using different $form_ids can implement hook_forms(), which maps
 *   different $form_id values to the proper form constructor function. Examples
 *   may be found in node_forms(), search_forms(), and user_forms().
 * @param ...
 *   Any additional arguments are passed on to the functions called by
 *   drupal_get_form(), including the unique form constructor function.
 *   For example, the node_edit form requires that a node object be passed
 *   in here when it is called. These are available to implementations of
 *   hook_form_alter() and hook_form_FORM_ID_alter() as the array
 *   $form['#parameters'].
 * @return
 *   The rendered form.
 */
function drupal_get_form($form_id) {
  $form_state = array(
    'storage' => NULL,
    'submitted' => FALSE,
  );
  $args = func_get_args();
  $cacheable = FALSE;
  if (isset($_SESSION['batch_form_state'])) {

    // We've been redirected here after a batch processing : the form has
    // already been processed, so we grab the post-process $form_state value
    // and move on to form display. See _batch_finished() function.
    $form_state = $_SESSION['batch_form_state'];
    unset($_SESSION['batch_form_state']);
  }
  else {

    // If the incoming $_POST contains a form_build_id, we'll check the
    // cache for a copy of the form in question. If it's there, we don't
    // have to rebuild the form to proceed. In addition, if there is stored
    // form_state data from a previous step, we'll retrieve it so it can
    // be passed on to the form processing code.
    if (isset($_POST['form_id']) && $_POST['form_id'] == $form_id && !empty($_POST['form_build_id'])) {
      $form = form_get_cache($_POST['form_build_id'], $form_state);
    }

    // If the previous bit of code didn't result in a populated $form
    // object, we're hitting the form for the first time and we need
    // to build it from scratch.
    if (!isset($form)) {
      $form_state['post'] = $_POST;

      // Use a copy of the function's arguments for manipulation
      $args_temp = $args;
      $args_temp[0] =& $form_state;
      array_unshift($args_temp, $form_id);
      $form = call_user_func_array('drupal_retrieve_form', $args_temp);
      $form_build_id = 'form-' . drupal_random_key();
      $form['#build_id'] = $form_build_id;
      drupal_prepare_form($form_id, $form, $form_state);

      // Store a copy of the unprocessed form for caching and indicate that it
      // is cacheable if #cache will be set.
      $original_form = $form;
      $cacheable = TRUE;
      unset($form_state['post']);
    }
    $form['#post'] = $_POST;

    // Now that we know we have a form, we'll process it (validating,
    // submitting, and handling the results returned by its submission
    // handlers. Submit handlers accumulate data in the form_state by
    // altering the $form_state variable, which is passed into them by
    // reference.
    drupal_process_form($form_id, $form, $form_state);
    if ($cacheable && !empty($form['#cache'])) {

      // Caching is done past drupal_process_form so #process callbacks can
      // set #cache.
      form_set_cache($form_build_id, $original_form, $form_state);
    }
  }

  // Most simple, single-step forms will be finished by this point --
  // drupal_process_form() usually redirects to another page (or to
  // a 'fresh' copy of the form) once processing is complete. If one
  // of the form's handlers has set $form_state['redirect'] to FALSE,
  // the form will simply be re-rendered with the values still in its
  // fields.
  //
  // If $form_state['storage'] or $form_state['rebuild'] has been set
  // and input has been processed, we know that we're in a complex
  // multi-part process of some sort and the form's workflow is NOT
  // complete. We need to construct a fresh copy of the form, passing
  // in the latest $form_state in addition to any other variables passed
  // into drupal_get_form().
  if ((!empty($form_state['storage']) || !empty($form_state['rebuild'])) && !empty($form_state['process_input']) && !form_get_errors()) {
    $form = drupal_rebuild_form($form_id, $form_state, $args);
  }

  // If we haven't redirected to a new location by now, we want to
  // render whatever form array is currently in hand.
  return drupal_render_form($form_id, $form);
}

/**
 * Retrieves a form, caches it and processes it with an empty $_POST.
 *
 * This function clears $_POST and passes the empty $_POST to the form_builder.
 * To preserve some parts from $_POST, pass them in $form_state.
 *
 * If your AHAH callback simulates the pressing of a button, then your AHAH
 * callback will need to do the same as what drupal_get_form would do when the
 * button is pressed: get the form from the cache, run drupal_process_form over
 * it and then if it needs rebuild, run drupal_rebuild_form over it. Then send
 * back a part of the returned form.
 * $form_state['clicked_button']['#array_parents'] will help you to find which
 * part.
 *
 * @param $form_id
 *   The unique string identifying the desired form. If a function
 *   with that name exists, it is called to build the form array.
 *   Modules that need to generate the same form (or very similar forms)
 *   using different $form_ids can implement hook_forms(), which maps
 *   different $form_id values to the proper form constructor function. Examples
 *   may be found in node_forms(), search_forms(), and user_forms().
 * @param $form_state
 *   A keyed array containing the current state of the form. Most
 *   important is the $form_state['storage'] collection.
 * @param $args
 *   Any additional arguments are passed on to the functions called by
 *   drupal_get_form(), plus the original form_state in the beginning. If you
 *   are getting a form from the cache, use $form['#parameters'] to shift off
 *   the $form_id from its beginning then the resulting array can be used as
 *   $arg here.
 * @param $form_build_id
 *   If the AHAH callback calling this function only alters part of the form,
 *   then pass in the existing form_build_id so we can re-cache with the same
 *   csid.
 * @return
 *   The newly built form.
 */
function drupal_rebuild_form($form_id, &$form_state, $args, $form_build_id = NULL) {

  // Remove the first argument. This is $form_id.when called from
  // drupal_get_form and the original $form_state when called from some AHAH
  // callback. Neither is needed. After that, put in the current state.
  $args[0] =& $form_state;

  // And the form_id.
  array_unshift($args, $form_id);
  $form = call_user_func_array('drupal_retrieve_form', $args);
  if (!isset($form_build_id)) {

    // We need a new build_id for the new version of the form.
    $form_build_id = 'form-' . drupal_random_key();
  }
  $form['#build_id'] = $form_build_id;
  drupal_prepare_form($form_id, $form, $form_state);

  // Now, we cache the form structure so it can be retrieved later for
  // validation. If $form_state['storage'] is populated, we'll also cache
  // it so that it can be used to resume complex multi-step processes.
  form_set_cache($form_build_id, $form, $form_state);

  // Clear out all post data, as we don't want the previous step's
  // data to pollute this one and trigger validate/submit handling,
  // then process the form for rendering.
  $_POST = array();
  $form['#post'] = array();
  drupal_process_form($form_id, $form, $form_state);
  return $form;
}

/**
 * Store a form in the cache.
 */
function form_set_cache($form_build_id, $form, $form_state) {
  global $user;

  // 6 hours cache life time for forms should be plenty.
  $expire = 21600;
  if ($user->uid) {
    $form['#cache_token'] = drupal_get_token();
  }
  elseif (variable_get('cache', CACHE_DISABLED) != CACHE_DISABLED && $_SERVER['REQUEST_METHOD'] == 'GET' && page_get_cache(TRUE)) {
    $form['#immutable'] = TRUE;
  }
  $form_build_id_old = $form_build_id;
  $form_build_id = form_build_id_map($form_build_id_old);
  cache_set('form_' . $form_build_id, $form, 'cache_form', time() + $expire);
  if (!empty($form_state['storage'])) {
    cache_set('storage_' . $form_build_id, $form_state['storage'], 'cache_form', time() + $expire);
  }

  // If form_set_cache is called in the context of an ahah handler inform the
  // client about the changed form build_id via the X-Drupal-Build-Id HTTP
  // header.
  if (!empty($_SERVER['HTTP_X_DRUPAL_ACCEPT_BUILD_ID']) && !empty($_POST['form_build_id']) && $_POST['form_build_id'] == $form_build_id_old && $form_build_id_old != $form_build_id) {
    drupal_set_header('X-Drupal-Build-Id: ' . $form_build_id);
  }
}

/**
 * Fetch a form from cache.
 */
function form_get_cache($form_build_id, &$form_state) {
  global $user;
  if ($cached = cache_get('form_' . $form_build_id, 'cache_form')) {
    $form = $cached->data;
    if (isset($form['#cache_token']) && drupal_valid_token($form['#cache_token']) || !isset($form['#cache_token']) && !$user->uid) {
      if ($cached = cache_get('storage_' . $form_build_id, 'cache_form')) {
        $form_state['storage'] = $cached->data;
      }

      // Generate a new #build_id if the cached form was rendered on a cacheable
      // page.
      if (!empty($form['#immutable'])) {
        $form['#build_id'] = 'form-' . drupal_random_key();
        $form['form_build_id']['#value'] = $form['#build_id'];
        $form['form_build_id']['#id'] = $form['#build_id'];
        unset($form['#immutable']);
        form_build_id_map($form_build_id, $form['#build_id']);
      }
      return $form;
    }
  }
}

/**
 * Maintain a map of immutable form_build_ids to cloned form.
 */
function form_build_id_map($form_build_id, $new_build_id = NULL) {
  static $build_id_map = array();
  if (isset($new_build_id) && isset($form_build_id)) {
    $build_id_map[$form_build_id] = $new_build_id;
  }
  return isset($build_id_map[$form_build_id]) ? $build_id_map[$form_build_id] : $form_build_id;
}

/**
 * Retrieves, populates, and processes a form.
 *
 * This function allows you to supply values for form elements and submit a
 * form for processing. Compare to drupal_get_form(), which also builds and
 * processes a form, but does not allow you to supply values.
 *
 * There is no return value, but you can check to see if there are errors by
 * calling form_get_errors().
 *
 * @param $form_id
 *   The unique string identifying the desired form. If a function
 *   with that name exists, it is called to build the form array.
 *   Modules that need to generate the same form (or very similar forms)
 *   using different $form_ids can implement hook_forms(), which maps
 *   different $form_id values to the proper form constructor function. Examples
 *   may be found in node_forms(), search_forms(), and user_forms().
 * @param $form_state
 *   A keyed array containing the current state of the form. Most
 *   important is the $form_state['values'] collection, a tree of data
 *   used to simulate the incoming $_POST information from a user's
 *   form submission.
 * @param ...
 *   Any additional arguments are passed on to the functions called by
 *   drupal_execute(), including the unique form constructor function.
 *   For example, the node_edit form requires that a node object be passed
 *   in here when it is called.
 * For example:
 * @code
 * // register a new user
 * $form_state = array();
 * $form_state['values']['name'] = 'robo-user';
 * $form_state['values']['mail'] = 'robouser@example.com';
 * $form_state['values']['pass']['pass1'] = 'password';
 * $form_state['values']['pass']['pass2'] = 'password';
 * $form_state['values']['op'] = t('Create new account');
 * drupal_execute('user_register', $form_state);
 *
 * // Create a new node
 * $form_state = array();
 * module_load_include('inc', 'node', 'node.pages');
 * $node = array('type' => 'story');
 * $form_state['values']['title'] = 'My node';
 * $form_state['values']['body'] = 'This is the body text!';
 * $form_state['values']['name'] = 'robo-user';
 * $form_state['values']['op'] = t('Save');
 * drupal_execute('story_node_form', $form_state, (object)$node);
 * @endcode
 */
function drupal_execute($form_id, &$form_state) {
  $args = func_get_args();

  // Make sure $form_state is passed around by reference.
  $args[1] =& $form_state;
  $form = call_user_func_array('drupal_retrieve_form', $args);
  $form['#post'] = $form_state['values'];

  // Reset form validation.
  $form_state['must_validate'] = TRUE;
  form_set_error(NULL, '', TRUE);
  drupal_prepare_form($form_id, $form, $form_state);
  drupal_process_form($form_id, $form, $form_state);
}

/**
 * Retrieves the structured array that defines a given form.
 *
 * @param $form_id
 *   The unique string identifying the desired form. If a function
 *   with that name exists, it is called to build the form array.
 *   Modules that need to generate the same form (or very similar forms)
 *   using different $form_ids can implement hook_forms(), which maps
 *   different $form_id values to the proper form constructor function.
 * @param $form_state
 *   A keyed array containing the current state of the form.
 * @param ...
 *   Any additional arguments needed by the unique form constructor
 *   function. Generally, these are any arguments passed into the
 *   drupal_get_form() or drupal_execute() functions after the first
 *   argument. If a module implements hook_forms(), it can examine
 *   these additional arguments and conditionally return different
 *   builder functions as well.
 */
function drupal_retrieve_form($form_id, &$form_state) {
  static $forms;

  // We save two copies of the incoming arguments: one for modules to use
  // when mapping form ids to constructor functions, and another to pass to
  // the constructor function itself. We shift out the first argument -- the
  // $form_id itself -- from the list to pass into the constructor function,
  // since it's already known.
  $args = func_get_args();
  $saved_args = $args;
  array_shift($args);
  if (isset($form_state)) {
    array_shift($args);
  }

  // We first check to see if there's a function named after the $form_id.
  // If there is, we simply pass the arguments on to it to get the form.
  if (!function_exists($form_id)) {

    // In cases where many form_ids need to share a central constructor function,
    // such as the node editing form, modules can implement hook_forms(). It
    // maps one or more form_ids to the correct constructor functions.
    //
    // We cache the results of that hook to save time, but that only works
    // for modules that know all their form_ids in advance. (A module that
    // adds a small 'rate this comment' form to each comment in a list
    // would need a unique form_id for each one, for example.)
    //
    // So, we call the hook if $forms isn't yet populated, OR if it doesn't
    // yet have an entry for the requested form_id.
    if (!isset($forms) || !isset($forms[$form_id])) {
      $forms = module_invoke_all('forms', $form_id, $args);
    }
    $form_definition = $forms[$form_id];
    if (isset($form_definition['callback arguments'])) {
      $args = array_merge($form_definition['callback arguments'], $args);
    }
    if (isset($form_definition['callback'])) {
      $callback = $form_definition['callback'];
    }
  }
  array_unshift($args, NULL);
  $args[0] =& $form_state;

  // If $callback was returned by a hook_forms() implementation, call it.
  // Otherwise, call the function named after the form id.
  $form = call_user_func_array(isset($callback) ? $callback : $form_id, $args);

  // We store the original function arguments, rather than the final $arg
  // value, so that form_alter functions can see what was originally
  // passed to drupal_retrieve_form(). This allows the contents of #parameters
  // to be saved and passed in at a later date to recreate the form.
  $form['#parameters'] = $saved_args;
  return $form;
}

/**
 * This function is the heart of form API. The form gets built, validated and in
 * appropriate cases, submitted.
 *
 * @param $form_id
 *   The unique string identifying the current form.
 * @param $form
 *   An associative array containing the structure of the form.
 * @param $form_state
 *   A keyed array containing the current state of the form. This
 *   includes the current persistent storage data for the form, and
 *   any data passed along by earlier steps when displaying a
 *   multi-step form. Additional information, like the sanitized $_POST
 *   data, is also accumulated here.
 */
function drupal_process_form($form_id, &$form, &$form_state) {
  $form_state['values'] = array();
  $form = form_builder($form_id, $form, $form_state);

  // Only process the form if it is programmed or the form_id coming
  // from the POST data is set and matches the current form_id.
  if (!empty($form['#programmed']) || !empty($form['#post']) && (isset($form['#post']['form_id']) && $form['#post']['form_id'] == $form_id)) {
    $form_state['process_input'] = TRUE;
    drupal_validate_form($form_id, $form, $form_state);

    // form_clean_id() maintains a cache of element IDs it has seen,
    // so it can prevent duplicates. We want to be sure we reset that
    // cache when a form is processed, so scenerios that result in
    // the form being built behind the scenes and again for the
    // browser don't increment all the element IDs needlessly.
    form_clean_id(NULL, TRUE);
    if (!empty($form_state['submitted']) && !form_get_errors() && empty($form_state['rebuild'])) {
      $form_state['redirect'] = NULL;
      form_execute_handlers('submit', $form, $form_state);

      // We'll clear out the cached copies of the form and its stored data
      // here, as we've finished with them. The in-memory copies are still
      // here, though.
      if (variable_get('cache', CACHE_DISABLED) == CACHE_DISABLED && !empty($form_state['values']['form_build_id'])) {
        cache_clear_all('form_' . $form_state['values']['form_build_id'], 'cache_form');
        cache_clear_all('storage_' . $form_state['values']['form_build_id'], 'cache_form');
      }

      // If batches were set in the submit handlers, we process them now,
      // possibly ending execution. We make sure we do not react to the batch
      // that is already being processed (if a batch operation performs a
      // drupal_execute).
      if (($batch =& batch_get()) && !isset($batch['current_set'])) {

        // The batch uses its own copies of $form and $form_state for
        // late execution of submit handers and post-batch redirection.
        $batch['form'] = $form;
        $batch['form_state'] = $form_state;
        $batch['progressive'] = !$form['#programmed'];
        batch_process();

        // Execution continues only for programmatic forms.
        // For 'regular' forms, we get redirected to the batch processing
        // page. Form redirection will be handled in _batch_finished(),
        // after the batch is processed.
      }

      // If no submit handlers have populated the $form_state['storage']
      // bundle, and the $form_state['rebuild'] flag has not been set,
      // we're finished and should redirect to a new destination page
      // if one has been set (and a fresh, unpopulated copy of the form
      // if one hasn't). If the form was called by drupal_execute(),
      // however, we'll skip this and let the calling function examine
      // the resulting $form_state bundle itself.
      if (!$form['#programmed'] && empty($form_state['rebuild']) && empty($form_state['storage'])) {
        drupal_redirect_form($form, $form_state['redirect']);
      }
    }
  }
}

/**
 * Prepares a structured form array by adding required elements,
 * executing any hook_form_alter functions, and optionally inserting
 * a validation token to prevent tampering.
 *
 * @param $form_id
 *   A unique string identifying the form for validation, submission,
 *   theming, and hook_form_alter functions.
 * @param $form
 *   An associative array containing the structure of the form.
 * @param $form_state
 *   A keyed array containing the current state of the form. Passed
 *   in here so that hook_form_alter() calls can use it, as well.
 */
function drupal_prepare_form($form_id, &$form, &$form_state) {
  global $user;
  $form['#type'] = 'form';
  $form['#programmed'] = isset($form['#post']);
  if (isset($form['#build_id'])) {
    $form['form_build_id'] = array(
      '#type' => 'hidden',
      '#value' => $form['#build_id'],
      '#id' => $form['#build_id'],
      '#name' => 'form_build_id',
    );
  }

  // Add a token, based on either #token or form_id, to any form displayed to
  // authenticated users. This ensures that any submitted form was actually
  // requested previously by the user and protects against cross site request
  // forgeries.
  if (isset($form['#token'])) {
    if ($form['#token'] === FALSE || $user->uid == 0 || $form['#programmed']) {
      unset($form['#token']);
    }
    else {
      $form['form_token'] = array(
        '#type' => 'token',
        '#default_value' => drupal_get_token($form['#token']),
      );
    }
  }
  else {
    if (isset($user->uid) && $user->uid && !$form['#programmed']) {
      $form['#token'] = $form_id;
      $form['form_token'] = array(
        '#id' => form_clean_id('edit-' . $form_id . '-form-token'),
        '#type' => 'token',
        '#default_value' => drupal_get_token($form['#token']),
      );
    }
  }
  if (isset($form_id)) {
    $form['form_id'] = array(
      '#type' => 'hidden',
      '#value' => $form_id,
      '#id' => form_clean_id("edit-{$form_id}"),
    );
  }
  if (!isset($form['#id'])) {
    $form['#id'] = form_clean_id($form_id);
  }
  $form += _element_info('form');
  if (!isset($form['#validate'])) {
    if (function_exists($form_id . '_validate')) {
      $form['#validate'] = array(
        $form_id . '_validate',
      );
    }
  }
  if (!isset($form['#submit'])) {
    if (function_exists($form_id . '_submit')) {

      // We set submit here so that it can be altered.
      $form['#submit'] = array(
        $form_id . '_submit',
      );
    }
  }

  // Normally, we would call drupal_alter($form_id, $form, $form_state).
  // However, drupal_alter() normally supports just one byref parameter. Using
  // the __drupal_alter_by_ref key, we can store any additional parameters
  // that need to be altered, and they'll be split out into additional params
  // for the hook_form_alter() implementations.
  // @todo: Remove this in Drupal 7.
  $data =& $form;
  $data['__drupal_alter_by_ref'] = array(
    &$form_state,
  );
  drupal_alter('form_' . $form_id, $data);

  // __drupal_alter_by_ref is unset in the drupal_alter() function, we need
  // to repopulate it to ensure both calls get the data.
  $data['__drupal_alter_by_ref'] = array(
    &$form_state,
  );
  drupal_alter('form', $data, $form_id);
}

/**
 * Validates user-submitted form data from the $form_state using
 * the validate functions defined in a structured form array.
 *
 * @param $form_id
 *   A unique string identifying the form for validation, submission,
 *   theming, and hook_form_alter functions.
 * @param $form
 *   An associative array containing the structure of the form.
 * @param $form_state
 *   A keyed array containing the current state of the form. The current
 *   user-submitted data is stored in $form_state['values'], though
 *   form validation functions are passed an explicit copy of the
 *   values for the sake of simplicity. Validation handlers can also
 *   $form_state to pass information on to submit handlers. For example:
 *     $form_state['data_for_submision'] = $data;
 *   This technique is useful when validation requires file parsing,
 *   web service requests, or other expensive requests that should
 *   not be repeated in the submission step.
 */
function drupal_validate_form($form_id, $form, &$form_state) {
  static $validated_forms = array();
  if (isset($validated_forms[$form_id]) && empty($form_state['must_validate'])) {
    return;
  }

  // If the session token was set by drupal_prepare_form(), ensure that it
  // matches the current user's session.
  if (isset($form['#token'])) {
    if (!drupal_valid_token($form_state['values']['form_token'], $form['#token']) || !empty($form_state['invalid_token'])) {

      // Setting this error will cause the form to fail validation.
      form_set_error('form_token', t('Validation error, please try again. If this error persists, please contact the site administrator.'));

      // Stop here and don't run any further validation handlers, because they
      // could invoke non-safe operations which opens the door for CSRF
      // vulnerabilities.
      $validated_forms[$form_id] = TRUE;
      return;
    }
  }
  _form_validate($form, $form_state, $form_id);
  $validated_forms[$form_id] = TRUE;
}

/**
 * Renders a structured form array into themed HTML.
 *
 * @param $form_id
 *   A unique string identifying the form for validation, submission,
 *   theming, and hook_form_alter functions.
 * @param $form
 *   An associative array containing the structure of the form.
 * @return
 *   A string containing the themed HTML.
 */
function drupal_render_form($form_id, &$form) {

  // Don't override #theme if someone already set it.
  if (!isset($form['#theme'])) {
    init_theme();
    $registry = theme_get_registry();
    if (isset($registry[$form_id])) {
      $form['#theme'] = $form_id;
    }
  }
  $output = drupal_render($form);
  return $output;
}

/**
 * Redirect the user to a URL after a form has been processed.
 *
 * @param $form
 *   An associative array containing the structure of the form.
 * @param $redirect
 *   An optional value containing the destination path to redirect
 *   to if none is specified by the form.
 */
function drupal_redirect_form($form, $redirect = NULL) {
  $goto = NULL;
  if (isset($redirect)) {
    $goto = $redirect;
  }
  if ($goto !== FALSE && isset($form['#redirect'])) {
    $goto = $form['#redirect'];
  }
  if (!isset($goto) || $goto !== FALSE) {
    if (isset($goto)) {
      if (is_array($goto)) {
        call_user_func_array('drupal_goto', $goto);
      }
      else {
        drupal_goto($goto);
      }
    }
    drupal_goto($_GET['q']);
  }
}

/**
 * Performs validation on form elements. First ensures required fields are
 * completed, #maxlength is not exceeded, and selected options were in the
 * list of options given to the user. Then calls user-defined validators.
 *
 * @param $elements
 *   An associative array containing the structure of the form.
 * @param $form_state
 *   A keyed array containing the current state of the form. The current
 *   user-submitted data is stored in $form_state['values'], though
 *   form validation functions are passed an explicit copy of the
 *   values for the sake of simplicity. Validation handlers can also
 *   $form_state to pass information on to submit handlers. For example:
 *     $form_state['data_for_submision'] = $data;
 *   This technique is useful when validation requires file parsing,
 *   web service requests, or other expensive requests that should
 *   not be repeated in the submission step.
 * @param $form_id
 *   A unique string identifying the form for validation, submission,
 *   theming, and hook_form_alter functions.
 */
function _form_validate($elements, &$form_state, $form_id = NULL) {
  static $complete_form;

  // Also used in the installer, pre-database setup.
  $t = get_t();

  // Recurse through all children.
  foreach (element_children($elements) as $key) {
    if (isset($elements[$key]) && $elements[$key]) {
      _form_validate($elements[$key], $form_state);
    }
  }

  // Validate the current input.
  if (!isset($elements['#validated']) || !$elements['#validated']) {
    if (isset($elements['#needs_validation'])) {

      // Make sure a value is passed when the field is required.
      // A simple call to empty() will not cut it here as some fields, like
      // checkboxes, can return a valid value of '0'. Instead, check the
      // length if it's a string, and the item count if it's an array.
      if ($elements['#required'] && (!count($elements['#value']) || is_string($elements['#value']) && strlen(trim($elements['#value'])) == 0)) {
        form_error($elements, $t('!name field is required.', array(
          '!name' => $elements['#title'],
        )));
      }

      // Verify that the value is not longer than #maxlength.
      if (isset($elements['#maxlength']) && drupal_strlen($elements['#value']) > $elements['#maxlength']) {
        form_error($elements, $t('!name cannot be longer than %max characters but is currently %length characters long.', array(
          '!name' => empty($elements['#title']) ? $elements['#parents'][0] : $elements['#title'],
          '%max' => $elements['#maxlength'],
          '%length' => drupal_strlen($elements['#value']),
        )));
      }
      if (isset($elements['#options']) && isset($elements['#value'])) {
        if ($elements['#type'] == 'select') {
          $options = form_options_flatten($elements['#options']);
        }
        else {
          $options = $elements['#options'];
        }
        if (is_array($elements['#value'])) {
          $value = $elements['#type'] == 'checkboxes' ? array_keys(array_filter($elements['#value'])) : $elements['#value'];
          foreach ($value as $v) {
            if (!isset($options[$v])) {
              form_error($elements, $t('An illegal choice has been detected. Please contact the site administrator.'));
              watchdog('form', 'Illegal choice %choice in !name element.', array(
                '%choice' => $v,
                '!name' => empty($elements['#title']) ? $elements['#parents'][0] : $elements['#title'],
              ), WATCHDOG_ERROR);
            }
          }
        }
        elseif (!isset($options[$elements['#value']])) {
          form_error($elements, $t('An illegal choice has been detected. Please contact the site administrator.'));
          watchdog('form', 'Illegal choice %choice in %name element.', array(
            '%choice' => $elements['#value'],
            '%name' => empty($elements['#title']) ? $elements['#parents'][0] : $elements['#title'],
          ), WATCHDOG_ERROR);
        }
      }
    }

    // Call user-defined form level validators and store a copy of the full
    // form so that element-specific validators can examine the entire structure
    // if necessary.
    if (isset($form_id)) {
      form_execute_handlers('validate', $elements, $form_state);
      $complete_form = $elements;
    }
    elseif (isset($elements['#element_validate'])) {
      foreach ($elements['#element_validate'] as $function) {
        if (function_exists($function)) {
          $function($elements, $form_state, $complete_form);
        }
      }
    }
    $elements['#validated'] = TRUE;
  }
}

/**
 * A helper function used to execute custom validation and submission
 * handlers for a given form. Button-specific handlers are checked
 * first. If none exist, the function falls back to form-level handlers.
 *
 * @param $type
 *   The type of handler to execute. 'validate' or 'submit' are the
 *   defaults used by Form API.
 * @param $form
 *   An associative array containing the structure of the form.
 * @param $form_state
 *   A keyed array containing the current state of the form. If the user
 *   submitted the form by clicking a button with custom handler functions
 *   defined, those handlers will be stored here.
 */
function form_execute_handlers($type, &$form, &$form_state) {
  $return = FALSE;
  if (isset($form_state[$type . '_handlers'])) {
    $handlers = $form_state[$type . '_handlers'];
  }
  elseif (isset($form['#' . $type])) {
    $handlers = $form['#' . $type];
  }
  else {
    $handlers = array();
  }
  foreach ($handlers as $function) {
    if (function_exists($function)) {

      // Check to see if a previous _submit handler has set a batch, but
      // make sure we do not react to a batch that is already being processed
      // (for instance if a batch operation performs a drupal_execute()).
      if ($type == 'submit' && ($batch =& batch_get()) && !isset($batch['current_set'])) {

        // Some previous _submit handler has set a batch. We store the call
        // in a special 'control' batch set, for execution at the correct
        // time during the batch processing workflow.
        $batch['sets'][] = array(
          'form_submit' => $function,
        );
      }
      else {
        $function($form, $form_state);
      }
      $return = TRUE;
    }
  }
  return $return;
}

/**
 * File an error against a form element.
 *
 * @param $name
 *   The name of the form element. If the #parents property of your form
 *   element is array('foo', 'bar', 'baz') then you may set an error on 'foo'
 *   or 'foo][bar][baz'. Setting an error on 'foo' sets an error for every
 *   element where the #parents array starts with 'foo'.
 * @param $message
 *   The error message to present to the user.
 * @param $reset
 *   Reset the form errors static cache.
 * @return
 *   Never use the return value of this function, use form_get_errors and
 *   form_get_error instead.
 */
function form_set_error($name = NULL, $message = '', $reset = FALSE) {
  static $form = array();
  if ($reset) {
    $form = array();
  }
  if (isset($name) && !isset($form[$name])) {
    $form[$name] = $message;
    if ($message) {
      drupal_set_message($message, 'error');
    }
  }
  return $form;
}

/**
 * Return an associative array of all errors.
 */
function form_get_errors() {
  $form = form_set_error();
  if (!empty($form)) {
    return $form;
  }
}

/**
 * Return the error message filed against the form with the specified name.
 */
function form_get_error($element) {
  $form = form_set_error();
  $key = $element['#parents'][0];
  if (isset($form[$key])) {
    return $form[$key];
  }
  $key = implode('][', $element['#parents']);
  if (isset($form[$key])) {
    return $form[$key];
  }
}

/**
 * Flag an element as having an error.
 */
function form_error(&$element, $message = '') {
  form_set_error(implode('][', $element['#parents']), $message);
}

/**
 * Walk through the structured form array, adding any required
 * properties to each element and mapping the incoming $_POST
 * data to the proper elements.
 *
 * @param $form_id
 *   A unique string identifying the form for validation, submission,
 *   theming, and hook_form_alter functions.
 * @param $form
 *   An associative array containing the structure of the form.
 * @param $form_state
 *   A keyed array containing the current state of the form. In this
 *   context, it is used to accumulate information about which button
 *   was clicked when the form was submitted, as well as the sanitized
 *   $_POST data.
 */
function form_builder($form_id, $form, &$form_state) {
  static $complete_form, $cache;

  // Initialize as unprocessed.
  $form['#processed'] = FALSE;

  // Use element defaults.
  if (!empty($form['#type']) && ($info = _element_info($form['#type']))) {

    // Overlay $info onto $form, retaining preexisting keys in $form.
    $form += $info;
  }

  // Special handling if we're on the top level form element.
  if (isset($form['#type']) && $form['#type'] == 'form') {
    $cache = NULL;
    $complete_form = $form;
    if (!empty($form['#programmed'])) {
      $form_state['submitted'] = TRUE;
    }
    else {

      // If the session token was set by drupal_prepare_form(), ensure that it
      // matches the current user's session before processing input.
      if (isset($form['#token']) && isset($form['#post']) && (isset($form['#post']['form_id']) && $form['#post']['form_id'] == $form_id)) {
        $form_state['invalid_token'] = FALSE;
        if (empty($form['#post']['form_token']) || !drupal_valid_token($form['#post']['form_token'], $form['#token'])) {

          // Setting this error will cause the form to fail validation.
          form_set_error('form_token', t('Validation error, please try again. If this error persists, please contact the site administrator.'));

          // This value is checked in _form_builder_handle_input_element().
          $form_state['invalid_token'] = TRUE;

          // Make sure file uploads do not get processed.
          $_FILES = array();
        }
      }
    }
  }
  if (isset($form['#input']) && $form['#input']) {
    _form_builder_handle_input_element($form_id, $form, $form_state, $complete_form);
  }
  $form['#defaults_loaded'] = TRUE;

  // We start off assuming all form elements are in the correct order.
  $form['#sorted'] = TRUE;

  // Recurse through all child elements.
  $count = 0;
  foreach (element_children($form) as $key) {
    $form[$key]['#post'] = $form['#post'];
    $form[$key]['#programmed'] = $form['#programmed'];

    // Don't squash an existing tree value.
    if (!isset($form[$key]['#tree'])) {
      $form[$key]['#tree'] = $form['#tree'];
    }

    // Deny access to child elements if parent is denied.
    if (isset($form['#access']) && !$form['#access']) {
      $form[$key]['#access'] = FALSE;
    }

    // Don't squash existing parents value.
    if (!isset($form[$key]['#parents'])) {

      // Check to see if a tree of child elements is present. If so,
      // continue down the tree if required.
      $form[$key]['#parents'] = $form[$key]['#tree'] && $form['#tree'] ? array_merge($form['#parents'], array(
        $key,
      )) : array(
        $key,
      );
      $array_parents = isset($form['#array_parents']) ? $form['#array_parents'] : array();
      $array_parents[] = $key;
      $form[$key]['#array_parents'] = $array_parents;
    }

    // Assign a decimal placeholder weight to preserve original array order.
    if (!isset($form[$key]['#weight'])) {
      $form[$key]['#weight'] = $count / 1000;
    }
    else {

      // If one of the child elements has a weight then we will need to sort
      // later.
      unset($form['#sorted']);
    }
    $form[$key] = form_builder($form_id, $form[$key], $form_state);
    $count++;
  }

  // The #after_build flag allows any piece of a form to be altered
  // after normal input parsing has been completed.
  if (isset($form['#after_build']) && !isset($form['#after_build_done'])) {
    foreach ($form['#after_build'] as $function) {
      $form = $function($form, $form_state);
      $form['#after_build_done'] = TRUE;
    }
  }

  // Now that we've processed everything, we can go back to handle the funky
  // Internet Explorer button-click scenario.
  _form_builder_ie_cleanup($form, $form_state);

  // We shoud keep the buttons array until the IE clean up function
  // has recognized the submit button so the form has been marked
  // as submitted. If we already know which button was submitted,
  // we don't need the array.
  if (!empty($form_state['submitted'])) {
    unset($form_state['buttons']);
  }

  // If some callback set #cache, we need to flip a static flag so later it
  // can be found.
  if (!empty($form['#cache'])) {
    $cache = $form['#cache'];
  }

  // We are on the top form, we can copy back #cache if it's set.
  if (isset($form['#type']) && $form['#type'] == 'form' && isset($cache)) {
    $form['#cache'] = TRUE;
  }
  return $form;
}

/**
 * Populate the #value and #name properties of input elements so they
 * can be processed and rendered. Also, execute any #process handlers
 * attached to a specific element.
 */
function _form_builder_handle_input_element($form_id, &$form, &$form_state, $complete_form) {
  static $safe_core_value_callbacks = array(
    'form_type_token_value',
    'form_type_textfield_value',
    'form_type_checkbox_value',
    'form_type_checkboxes_value',
    'form_type_password_confirm_value',
    'form_type_select_value',
  );
  if (!isset($form['#name'])) {
    $name = array_shift($form['#parents']);
    $form['#name'] = $name;
    if ($form['#type'] == 'file') {

      // To make it easier to handle $_FILES in file.inc, we place all
      // file fields in the 'files' array. Also, we do not support
      // nested file names.
      $form['#name'] = 'files[' . $form['#name'] . ']';
    }
    elseif (count($form['#parents'])) {
      $form['#name'] .= '[' . implode('][', $form['#parents']) . ']';
    }
    array_unshift($form['#parents'], $name);
  }
  if (!isset($form['#id'])) {
    $form['#id'] = form_clean_id('edit-' . implode('-', $form['#parents']));
  }
  if (!empty($form['#disabled'])) {
    $form['#attributes']['disabled'] = 'disabled';
  }

  // With JavaScript or other easy hacking, input can be submitted even for
  // elements with #access=FALSE. For security, these must not be processed.
  // For pages with multiple forms, ensure that input is only processed for the
  // submitted form. drupal_execute() may bypass these checks and be treated as
  // a high privilege user submitting a single form.
  $process_input = $form['#programmed'] || (!isset($form['#access']) || $form['#access']) && isset($form['#post']) && (isset($form['#post']['form_id']) && $form['#post']['form_id'] == $form_id);
  if (!isset($form['#value']) && !array_key_exists('#value', $form)) {
    $function = !empty($form['#value_callback']) ? $form['#value_callback'] : 'form_type_' . $form['#type'] . '_value';
    if ($process_input) {
      $edit = $form['#post'];
      foreach ($form['#parents'] as $parent) {
        $edit = isset($edit[$parent]) ? $edit[$parent] : NULL;
      }
      if (!$form['#programmed'] || isset($edit)) {

        // Call #type_value to set the form value;
        if (function_exists($function)) {

          // Skip all value callbacks except safe ones like text if the CSRF
          // token was invalid.
          if (empty($form_state['invalid_token']) || in_array($function, $safe_core_value_callbacks)) {
            $form['#value'] = $function($form, $edit);
          }
          else {
            $edit = NULL;
          }
        }
        if (!isset($form['#value']) && isset($edit)) {
          $form['#value'] = $edit;
        }
      }

      // Mark all posted values for validation.
      if (isset($form['#value']) || isset($form['#required']) && $form['#required']) {
        $form['#needs_validation'] = TRUE;
      }
    }

    // Load defaults.
    if (!isset($form['#value'])) {

      // Call #type_value without a second argument to request default_value handling.
      if (function_exists($function)) {
        $form['#value'] = $function($form);
      }

      // Final catch. If we haven't set a value yet, use the explicit default value.
      // Avoid image buttons (which come with garbage value), so we only get value
      // for the button actually clicked.
      if (!isset($form['#value']) && empty($form['#has_garbage_value'])) {
        $form['#value'] = isset($form['#default_value']) ? $form['#default_value'] : '';
      }
    }
  }

  // Determine which button (if any) was clicked to submit the form.
  // We compare the incoming values with the buttons defined in the form,
  // and flag the one that matches. We have to do some funky tricks to
  // deal with Internet Explorer's handling of single-button forms, though.
  if ($process_input && !empty($form['#post']) && isset($form['#executes_submit_callback'])) {

    // First, accumulate a collection of buttons, divided into two bins:
    // those that execute full submit callbacks and those that only validate.
    $button_type = $form['#executes_submit_callback'] ? 'submit' : 'button';
    $form_state['buttons'][$button_type][] = $form;
    if (_form_button_was_clicked($form)) {
      $form_state['submitted'] = $form_state['submitted'] || $form['#executes_submit_callback'];

      // In most cases, we want to use form_set_value() to manipulate
      // the global variables. In this special case, we want to make sure that
      // the value of this element is listed in $form_variables under 'op'.
      $form_state['values'][$form['#name']] = $form['#value'];
      $form_state['clicked_button'] = $form;
      if (isset($form['#validate'])) {
        $form_state['validate_handlers'] = $form['#validate'];
      }
      if (isset($form['#submit'])) {
        $form_state['submit_handlers'] = $form['#submit'];
      }
    }
  }

  // Allow for elements to expand to multiple elements, e.g., radios,
  // checkboxes and files.
  if (isset($form['#process']) && !$form['#processed']) {
    foreach ($form['#process'] as $process) {
      if (function_exists($process)) {
        $form = $process($form, isset($edit) ? $edit : NULL, $form_state, $complete_form);
      }
    }
    $form['#processed'] = TRUE;
  }
  form_set_value($form, $form['#value'], $form_state);
}

/**
 * Helper function to handle the sometimes-convoluted logic of button
 * click detection.
 *
 * In Internet Explorer, if ONLY one submit button is present, AND the
 * enter key is used to submit the form, no form value is sent for it
 * and we'll never detect a match. That special case is handled by
 * _form_builder_ie_cleanup().
 */
function _form_button_was_clicked($form) {

  // First detect normal 'vanilla' button clicks. Traditionally, all
  // standard buttons on a form share the same name (usually 'op'),
  // and the specific return value is used to determine which was
  // clicked. This ONLY works as long as $form['#name'] puts the
  // value at the top level of the tree of $_POST data.
  if (isset($form['#post'][$form['#name']]) && $form['#post'][$form['#name']] == $form['#value']) {
    return TRUE;
  }
  elseif (!empty($form['#has_garbage_value']) && isset($form['#value']) && $form['#value'] !== '') {
    return TRUE;
  }
  return FALSE;
}

/**
 * In IE, if only one submit button is present, AND the enter key is
 * used to submit the form, no form value is sent for it and our normal
 * button detection code will never detect a match. We call this
 * function after all other button-detection is complete to check
 * for the proper conditions, and treat the single button on the form
 * as 'clicked' if they are met.
 */
function _form_builder_ie_cleanup($form, &$form_state) {

  // Quick check to make sure we're always looking at the full form
  // and not a sub-element.
  if (!empty($form['#type']) && $form['#type'] == 'form') {

    // If we haven't recognized a submission yet, and there's a single
    // submit button, we know that we've hit the right conditions. Grab
    // the first one and treat it as the clicked button.
    if (empty($form_state['submitted']) && !empty($form_state['buttons']['submit']) && empty($form_state['buttons']['button'])) {
      $button = $form_state['buttons']['submit'][0];

      // Set up all the $form_state information that would have been
      // populated had the button been recognized earlier.
      $form_state['submitted'] = TRUE;
      $form_state['submit_handlers'] = empty($button['#submit']) ? NULL : $button['#submit'];
      $form_state['validate_handlers'] = empty($button['#validate']) ? NULL : $button['#validate'];
      $form_state['values'][$button['#name']] = $button['#value'];
      $form_state['clicked_button'] = $button;
    }
  }
}

/**
 * Helper function to determine the value for an image button form element.
 *
 * @param $form
 *   The form element whose value is being populated.
 * @param $edit
 *   The incoming POST data to populate the form element. If this is FALSE,
 *   the element's default value should be returned.
 * @return
 *   The data that will appear in the $form_state['values'] collection
 *   for this element. Return nothing to use the default.
 */
function form_type_image_button_value($form, $edit = FALSE) {
  if ($edit !== FALSE) {
    if (!empty($edit)) {

      // If we're dealing with Mozilla or Opera, we're lucky. It will
      // return a proper value, and we can get on with things.
      return $form['#return_value'];
    }
    else {

      // Unfortunately, in IE we never get back a proper value for THIS
      // form element. Instead, we get back two split values: one for the
      // X and one for the Y coordinates on which the user clicked the
      // button. We'll find this element in the #post data, and search
      // in the same spot for its name, with '_x'.
      $post = $form['#post'];
      foreach (split('\\[', $form['#name']) as $element_name) {

        // chop off the ] that may exist.
        if (substr($element_name, -1) == ']') {
          $element_name = substr($element_name, 0, -1);
        }
        if (!isset($post[$element_name])) {
          if (isset($post[$element_name . '_x'])) {
            return $form['#return_value'];
          }
          return NULL;
        }
        $post = $post[$element_name];
      }
      return $form['#return_value'];
    }
  }
}

/**
 * Helper function to determine the value for a checkbox form element.
 *
 * @param $form
 *   The form element whose value is being populated.
 * @param $edit
 *   The incoming POST data to populate the form element. If this is FALSE,
 *   the element's default value should be returned.
 * @return
 *   The data that will appear in the $form_state['values'] collection
 *   for this element. Return nothing to use the default.
 */
function form_type_checkbox_value($form, $edit = FALSE) {
  if ($edit !== FALSE) {
    if (empty($form['#disabled'])) {
      return !empty($edit) ? $form['#return_value'] : 0;
    }
    else {
      return $form['#default_value'];
    }
  }
}

/**
 * Helper function to determine the value for a checkboxes form element.
 *
 * @param $form
 *   The form element whose value is being populated.
 * @param $edit
 *   The incoming POST data to populate the form element. If this is FALSE,
 *   the element's default value should be returned.
 * @return
 *   The data that will appear in the $form_state['values'] collection
 *   for this element. Return nothing to use the default.
 */
function form_type_checkboxes_value($form, $edit = FALSE) {
  if ($edit === FALSE) {
    $value = array();
    $form += array(
      '#default_value' => array(),
    );
    foreach ($form['#default_value'] as $key) {
      $value[$key] = 1;
    }
    return $value;
  }
  elseif (!isset($edit)) {
    return array();
  }
}

/**
 * Helper function to determine the value for a password_confirm form
 * element.
 *
 * @param $form
 *   The form element whose value is being populated.
 * @param $edit
 *   The incoming POST data to populate the form element. If this is FALSE,
 *   the element's default value should be returned.
 * @return
 *   The data that will appear in the $form_state['values'] collection
 *   for this element. Return nothing to use the default.
 */
function form_type_password_confirm_value($form, $edit = FALSE) {
  if ($edit === FALSE) {
    $form += array(
      '#default_value' => array(),
    );
    return $form['#default_value'] + array(
      'pass1' => '',
      'pass2' => '',
    );
  }
}

/**
 * Helper function to determine the value for a select form element.
 *
 * @param $form
 *   The form element whose value is being populated.
 * @param $edit
 *   The incoming POST data to populate the form element. If this is FALSE,
 *   the element's default value should be returned.
 * @return
 *   The data that will appear in the $form_state['values'] collection
 *   for this element. Return nothing to use the default.
 */
function form_type_select_value($form, $edit = FALSE) {
  if ($edit !== FALSE) {
    if (isset($form['#multiple']) && $form['#multiple']) {
      return is_array($edit) ? drupal_map_assoc($edit) : array();
    }
    else {
      return $edit;
    }
  }
}

/**
 * Helper function to determine the value for a textfield form element.
 *
 * @param $form
 *   The form element whose value is being populated.
 * @param $edit
 *   The incoming POST data to populate the form element. If this is FALSE,
 *   the element's default value should be returned.
 * @return
 *   The data that will appear in the $form_state['values'] collection
 *   for this element. Return nothing to use the default.
 */
function form_type_textfield_value($form, $edit = FALSE) {
  if ($edit !== FALSE) {

    // Equate $edit to the form value to ensure it's marked for
    // validation.
    return str_replace(array(
      "\r",
      "\n",
    ), '', $edit);
  }
}

/**
 * Helper function to determine the value for form's token value.
 *
 * @param $form
 *   The form element whose value is being populated.
 * @param $edit
 *   The incoming POST data to populate the form element. If this is FALSE,
 *   the element's default value should be returned.
 * @return
 *   The data that will appear in the $form_state['values'] collection
 *   for this element. Return nothing to use the default.
 */
function form_type_token_value($form, $edit = FALSE) {
  if ($edit !== FALSE) {
    return (string) $edit;
  }
}

/**
 * Change submitted form values during the form processing cycle.
 *
 * Use this function to change the submitted value of a form item in the
 * validation phase so that it persists in $form_state through to the
 * submission handlers in the submission phase.
 *
 * Since $form_state['values'] can either be a flat array of values, or a tree
 * of nested values, some care must be taken when using this function.
 * Specifically, $form_item['#parents'] is an array that describes the branch of
 * the tree whose value should be updated. For example, if we wanted to update
 * $form_state['values']['one']['two'] to 'new value', we'd pass in
 * $form_item['#parents'] = array('one', 'two') and $value = 'new value'.
 *
 * @param $form_item
 *   The form item that should have its value updated. Keys used: #parents,
 *   #value. In most cases you can just pass in the right element from the $form
 *   array.
 * @param $value
 *   The new value for the form item.
 * @param $form_state
 *   The array where the value change should be recorded.
 */
function form_set_value($form_item, $value, &$form_state) {
  _form_set_value($form_state['values'], $form_item, $form_item['#parents'], $value);
}

/**
 * Helper function for form_set_value().
 *
 * We iterate over $parents and create nested arrays for them
 * in $form_state['values'] if needed. Then we insert the value into
 * the right array.
 */
function _form_set_value(&$form_values, $form_item, $parents, $value) {
  $parent = array_shift($parents);
  if (empty($parents)) {
    $form_values[$parent] = $value;
  }
  else {
    if (!isset($form_values[$parent])) {
      $form_values[$parent] = array();
    }
    _form_set_value($form_values[$parent], $form_item, $parents, $value);
  }
}

/**
 * Retrieve the default properties for the defined element type.
 */
function _element_info($type, $refresh = NULL) {
  static $cache;
  $basic_defaults = array(
    '#description' => NULL,
    '#attributes' => array(),
    '#required' => FALSE,
    '#tree' => FALSE,
    '#parents' => array(),
  );
  if (!isset($cache) || $refresh) {
    $cache = array();
    foreach (module_implements('elements') as $module) {
      $elements = module_invoke($module, 'elements');
      if (isset($elements) && is_array($elements)) {
        $cache = array_merge_recursive($cache, $elements);
      }
    }
    if (sizeof($cache)) {
      foreach ($cache as $element_type => $info) {
        $cache[$element_type] = array_merge_recursive($basic_defaults, $info);
      }
    }
  }
  return $cache[$type];
}
function form_options_flatten($array, $reset = TRUE) {
  static $return;
  if ($reset) {
    $return = array();
  }
  foreach ($array as $key => $value) {
    if (is_object($value)) {
      form_options_flatten($value->option, FALSE);
    }
    else {
      if (is_array($value)) {
        form_options_flatten($value, FALSE);
      }
      else {
        $return[$key] = 1;
      }
    }
  }
  return $return;
}

/**
 * Format a dropdown menu or scrolling selection box.
 *
 * @param $element
 *   An associative array containing the properties of the element.
 *   Properties used: title, value, options, description, extra, multiple, required
 * @return
 *   A themed HTML string representing the form element.
 *
 * @ingroup themeable
 *
 * It is possible to group options together; to do this, change the format of
 * $options to an associative array in which the keys are group labels, and the
 * values are associative arrays in the normal $options format.
 */
function theme_select($element) {
  $select = '';
  $size = $element['#size'] ? ' size="' . $element['#size'] . '"' : '';
  _form_set_class($element, array(
    'form-select',
  ));
  $multiple = $element['#multiple'];
  return theme('form_element', $element, '<select name="' . $element['#name'] . '' . ($multiple ? '[]' : '') . '"' . ($multiple ? ' multiple="multiple" ' : '') . drupal_attributes($element['#attributes']) . ' id="' . $element['#id'] . '" ' . $size . '>' . form_select_options($element) . '</select>');
}
function form_select_options($element, $choices = NULL) {
  if (!isset($choices)) {
    $choices = $element['#options'];
  }

  // array_key_exists() accommodates the rare event where $element['#value'] is NULL.
  // isset() fails in this situation.
  $value_valid = isset($element['#value']) || array_key_exists('#value', $element);
  $value_is_array = is_array($element['#value']);
  $options = '';
  foreach ($choices as $key => $choice) {
    if (is_array($choice)) {
      $options .= '<optgroup label="' . check_plain($key) . '">';
      $options .= form_select_options($element, $choice);
      $options .= '</optgroup>';
    }
    elseif (is_object($choice)) {
      $options .= form_select_options($element, $choice->option);
    }
    else {
      $key = (string) $key;
      if ($value_valid && (!$value_is_array && (string) $element['#value'] === $key || $value_is_array && in_array($key, $element['#value']))) {
        $selected = ' selected="selected"';
      }
      else {
        $selected = '';
      }
      $options .= '<option value="' . check_plain($key) . '"' . $selected . '>' . check_plain($choice) . '</option>';
    }
  }
  return $options;
}

/**
 * Traverses a select element's #option array looking for any values
 * that hold the given key. Returns an array of indexes that match.
 *
 * This function is useful if you need to modify the options that are
 * already in a form element; for example, to remove choices which are
 * not valid because of additional filters imposed by another module.
 * One example might be altering the choices in a taxonomy selector.
 * To correctly handle the case of a multiple hierarchy taxonomy,
 * #options arrays can now hold an array of objects, instead of a
 * direct mapping of keys to labels, so that multiple choices in the
 * selector can have the same key (and label). This makes it difficult
 * to manipulate directly, which is why this helper function exists.
 *
 * This function does not support optgroups (when the elements of the
 * #options array are themselves arrays), and will return FALSE if
 * arrays are found. The caller must either flatten/restore or
 * manually do their manipulations in this case, since returning the
 * index is not sufficient, and supporting this would make the
 * "helper" too complicated and cumbersome to be of any help.
 *
 * As usual with functions that can return array() or FALSE, do not
 * forget to use === and !== if needed.
 *
 * @param $element
 *   The select element to search.
 * @param $key
 *   The key to look for.
 * @return
 *   An array of indexes that match the given $key. Array will be
 *   empty if no elements were found. FALSE if optgroups were found.
 */
function form_get_options($element, $key) {
  $keys = array();
  foreach ($element['#options'] as $index => $choice) {
    if (is_array($choice)) {
      return FALSE;
    }
    else {
      if (is_object($choice)) {
        if (isset($choice->option[$key])) {
          $keys[] = $index;
        }
      }
      else {
        if ($index == $key) {
          $keys[] = $index;
        }
      }
    }
  }
  return $keys;
}

/**
 * Format a group of form items.
 *
 * @param $element
 *   An associative array containing the properties of the element.
 *   Properties used: attributes, title, value, description, children, collapsible, collapsed
 * @return
 *   A themed HTML string representing the form item group.
 *
 * @ingroup themeable
 */
function theme_fieldset($element) {
  if (!empty($element['#collapsible'])) {
    drupal_add_js('misc/collapse.js');
    if (!isset($element['#attributes']['class'])) {
      $element['#attributes']['class'] = '';
    }
    $element['#attributes']['class'] .= ' collapsible';
    if (!empty($element['#collapsed'])) {
      $element['#attributes']['class'] .= ' collapsed';
    }
  }
  return '<fieldset' . drupal_attributes($element['#attributes']) . '>' . ($element['#title'] ? '<legend>' . $element['#title'] . '</legend>' : '') . (isset($element['#description']) && $element['#description'] ? '<div class="description">' . $element['#description'] . '</div>' : '') . (!empty($element['#children']) ? $element['#children'] : '') . (isset($element['#value']) ? $element['#value'] : '') . "</fieldset>\n";
}

/**
 * Format a radio button.
 *
 * @param $element
 *   An associative array containing the properties of the element.
 *   Properties used: required, return_value, value, attributes, title, description
 * @return
 *   A themed HTML string representing the form item group.
 *
 * @ingroup themeable
 */
function theme_radio($element) {
  _form_set_class($element, array(
    'form-radio',
  ));
  $output = '<input type="radio" ';
  $output .= 'id="' . $element['#id'] . '" ';
  $output .= 'name="' . $element['#name'] . '" ';
  $output .= 'value="' . $element['#return_value'] . '" ';
  $output .= check_plain($element['#value']) == $element['#return_value'] ? ' checked="checked" ' : ' ';
  $output .= drupal_attributes($element['#attributes']) . ' />';
  if (!is_null($element['#title'])) {
    $output = '<label class="option" for="' . $element['#id'] . '">' . $output . ' ' . $element['#title'] . '</label>';
  }
  unset($element['#title']);
  return theme('form_element', $element, $output);
}

/**
 * Format a set of radio buttons.
 *
 * @param $element
 *   An associative array containing the properties of the element.
 *   Properties used: title, value, options, description, required and attributes.
 * @return
 *   A themed HTML string representing the radio button set.
 *
 * @ingroup themeable
 */
function theme_radios($element) {
  $class = 'form-radios';
  if (isset($element['#attributes']['class'])) {
    $class .= ' ' . $element['#attributes']['class'];
  }
  $element['#children'] = '<div class="' . $class . '">' . (!empty($element['#children']) ? $element['#children'] : '') . '</div>';
  if ($element['#title'] || $element['#description']) {
    unset($element['#id']);
    return theme('form_element', $element, $element['#children']);
  }
  else {
    return $element['#children'];
  }
}

/**
 * Format a password_confirm item.
 *
 * @param $element
 *   An associative array containing the properties of the element.
 *   Properties used: title, value, id, required, error.
 * @return
 *   A themed HTML string representing the form item.
 *
 * @ingroup themeable
 */
function theme_password_confirm($element) {
  return theme('form_element', $element, $element['#children']);
}

/**
 * Expand a password_confirm field into two text boxes.
 */
function expand_password_confirm($element) {
  $element['pass1'] = array(
    '#type' => 'password',
    '#title' => t('Password'),
    '#value' => empty($element['#value']) ? NULL : $element['#value']['pass1'],
    '#required' => $element['#required'],
    '#attributes' => array(
      'class' => 'password-field',
    ),
  );
  $element['pass2'] = array(
    '#type' => 'password',
    '#title' => t('Confirm password'),
    '#value' => empty($element['#value']) ? NULL : $element['#value']['pass2'],
    '#required' => $element['#required'],
    '#attributes' => array(
      'class' => 'password-confirm',
    ),
  );
  $element['#element_validate'] = array(
    'password_confirm_validate',
  );
  $element['#tree'] = TRUE;
  if (isset($element['#size'])) {
    $element['pass1']['#size'] = $element['pass2']['#size'] = $element['#size'];
  }
  return $element;
}

/**
 * Validate password_confirm element.
 */
function password_confirm_validate($form, &$form_state) {
  $pass1 = trim($form['pass1']['#value']);
  if (!empty($pass1)) {
    $pass2 = trim($form['pass2']['#value']);
    if (strcmp($pass1, $pass2)) {
      form_error($form, t('The specified passwords do not match.'));
    }
  }
  elseif ($form['#required'] && !empty($form['#post'])) {
    form_error($form, t('Password field is required.'));
  }

  // Password field must be converted from a two-element array into a single
  // string regardless of validation results.
  form_set_value($form['pass1'], NULL, $form_state);
  form_set_value($form['pass2'], NULL, $form_state);
  form_set_value($form, $pass1, $form_state);
  return $form;
}

/**
 * Format a date selection element.
 *
 * @param $element
 *   An associative array containing the properties of the element.
 *   Properties used: title, value, options, description, required and attributes.
 * @return
 *   A themed HTML string representing the date selection boxes.
 *
 * @ingroup themeable
 */
function theme_date($element) {
  return theme('form_element', $element, '<div class="container-inline">' . $element['#children'] . '</div>');
}

/**
 * Roll out a single date element.
 */
function expand_date($element) {

  // Default to current date
  if (empty($element['#value'])) {
    $element['#value'] = array(
      'day' => format_date(time(), 'custom', 'j'),
      'month' => format_date(time(), 'custom', 'n'),
      'year' => format_date(time(), 'custom', 'Y'),
    );
  }
  $element['#tree'] = TRUE;

  // Determine the order of day, month, year in the site's chosen date format.
  $format = variable_get('date_format_short', 'm/d/Y - H:i');
  $sort = array();
  $sort['day'] = max(strpos($format, 'd'), strpos($format, 'j'));
  $sort['month'] = max(strpos($format, 'm'), strpos($format, 'M'));
  $sort['year'] = strpos($format, 'Y');
  asort($sort);
  $order = array_keys($sort);

  // Output multi-selector for date.
  foreach ($order as $type) {
    switch ($type) {
      case 'day':
        $options = drupal_map_assoc(range(1, 31));
        break;
      case 'month':
        $options = drupal_map_assoc(range(1, 12), 'map_month');
        break;
      case 'year':
        $options = drupal_map_assoc(range(1900, 2050));
        break;
    }
    $parents = $element['#parents'];
    $parents[] = $type;
    $element[$type] = array(
      '#type' => 'select',
      '#value' => $element['#value'][$type],
      '#attributes' => $element['#attributes'],
      '#options' => $options,
    );
  }
  return $element;
}

/**
 * Validates the date type to stop dates like February 30, 2006.
 */
function date_validate($element) {
  if (!checkdate($element['#value']['month'], $element['#value']['day'], $element['#value']['year'])) {
    form_error($element, t('The specified date is invalid.'));
  }
}

/**
 * Helper function for usage with drupal_map_assoc to display month names.
 */
function map_month($month) {
  return format_date(gmmktime(0, 0, 0, $month, 2, 1970), 'custom', 'M', 0);
}

/**
 * If no default value is set for weight select boxes, use 0.
 */
function weight_value(&$form) {
  if (isset($form['#default_value'])) {
    $form['#value'] = $form['#default_value'];
  }
  else {
    $form['#value'] = 0;
  }
}

/**
 * Roll out a single radios element to a list of radios,
 * using the options array as index.
 */
function expand_radios($element) {
  if (count($element['#options']) > 0) {
    foreach ($element['#options'] as $key => $choice) {
      if (!isset($element[$key])) {

        // Generate the parents as the autogenerator does, so we will have a
        // unique id for each radio button.
        $parents_for_id = array_merge($element['#parents'], array(
          $key,
        ));
        $element[$key] = array(
          '#type' => 'radio',
          '#title' => $choice,
          '#return_value' => check_plain($key),
          '#default_value' => isset($element['#default_value']) ? $element['#default_value'] : NULL,
          '#attributes' => $element['#attributes'],
          '#parents' => $element['#parents'],
          '#id' => form_clean_id('edit-' . implode('-', $parents_for_id)),
          '#ahah' => isset($element['#ahah']) ? $element['#ahah'] : NULL,
        );
      }
    }
  }
  return $element;
}

/**
 * Add AHAH information about a form element to the page to communicate with
 * javascript. If #ahah[path] is set on an element, this additional javascript is
 * added to the page header to attach the AHAH behaviors. See ahah.js for more
 * information.
 *
 * @param $element
 *   An associative array containing the properties of the element.
 *   Properties used: ahah_event, ahah_path, ahah_wrapper, ahah_parameters,
 *   ahah_effect.
 * @return
 *   None. Additional code is added to the header of the page using
 *   drupal_add_js.
 */
function form_expand_ahah($element) {
  global $user;
  static $js_added = array();

  // Add a reasonable default event handler if none specified.
  if (isset($element['#ahah']['path']) && !isset($element['#ahah']['event'])) {
    switch ($element['#type']) {
      case 'submit':
      case 'button':
      case 'image_button':

        // Use the mousedown instead of the click event because form
        // submission via pressing the enter key triggers a click event on
        // submit inputs, inappropriately triggering AHAH behaviors.
        $element['#ahah']['event'] = 'mousedown';

        // Attach an additional event handler so that AHAH behaviours
        // can be triggered still via keyboard input.
        $element['#ahah']['keypress'] = TRUE;
        break;
      case 'password':
      case 'textfield':
      case 'textarea':
        $element['#ahah']['event'] = 'blur';
        break;
      case 'radio':
      case 'checkbox':
      case 'select':
        $element['#ahah']['event'] = 'change';
        break;
    }
  }

  // Adding the same javascript settings twice will cause a recursion error,
  // we avoid the problem by checking if the javascript has already been added.
  if (isset($element['#ahah']['path']) && isset($element['#ahah']['event']) && !isset($js_added[$element['#id']])) {
    drupal_add_js('misc/jquery.form.js');
    drupal_add_js('misc/ahah.js');
    $ahah_binding = array(
      'url' => url($element['#ahah']['path']),
      'event' => $element['#ahah']['event'],
      'keypress' => empty($element['#ahah']['keypress']) ? NULL : $element['#ahah']['keypress'],
      'wrapper' => empty($element['#ahah']['wrapper']) ? NULL : $element['#ahah']['wrapper'],
      'selector' => empty($element['#ahah']['selector']) ? '#' . $element['#id'] : $element['#ahah']['selector'],
      'effect' => empty($element['#ahah']['effect']) ? 'none' : $element['#ahah']['effect'],
      'method' => empty($element['#ahah']['method']) ? 'replace' : $element['#ahah']['method'],
      'progress' => empty($element['#ahah']['progress']) ? array(
        'type' => 'throbber',
      ) : $element['#ahah']['progress'],
      'button' => isset($element['#executes_submit_callback']) ? array(
        $element['#name'] => $element['#value'],
      ) : FALSE,
    );

    // If page caching is active, indicate that this form is immutable.
    if (variable_get('cache', CACHE_DISABLED) != CACHE_DISABLED && !$user->uid && $_SERVER['REQUEST_METHOD'] == 'GET' && page_get_cache(TRUE)) {
      $ahah_binding['immutable'] = TRUE;
    }

    // Convert a simple #ahah[progress] type string into an array.
    if (is_string($ahah_binding['progress'])) {
      $ahah_binding['progress'] = array(
        'type' => $ahah_binding['progress'],
      );
    }

    // Change progress path to a full URL.
    if (isset($ahah_binding['progress']['path'])) {
      $ahah_binding['progress']['url'] = url($ahah_binding['progress']['path']);
    }

    // Add progress.js if we're doing a bar display.
    if ($ahah_binding['progress']['type'] == 'bar') {
      drupal_add_js('misc/progress.js');
    }
    drupal_add_js(array(
      'ahah' => array(
        $element['#id'] => $ahah_binding,
      ),
    ), 'setting');
    $js_added[$element['#id']] = TRUE;
    $element['#cache'] = TRUE;
  }
  return $element;
}

/**
 * Format a form item.
 *
 * @param $element
 *   An associative array containing the properties of the element.
 *   Properties used:  title, value, description, required, error
 * @return
 *   A themed HTML string representing the form item.
 *
 * @ingroup themeable
 */
function theme_item($element) {
  return theme('form_element', $element, $element['#value'] . (!empty($element['#children']) ? $element['#children'] : ''));
}

/**
 * Format a checkbox.
 *
 * @param $element
 *   An associative array containing the properties of the element.
 *   Properties used:  title, value, return_value, description, required
 * @return
 *   A themed HTML string representing the checkbox.
 *
 * @ingroup themeable
 */
function theme_checkbox($element) {
  _form_set_class($element, array(
    'form-checkbox',
  ));
  $checkbox = '<input ';
  $checkbox .= 'type="checkbox" ';
  $checkbox .= 'name="' . $element['#name'] . '" ';
  $checkbox .= 'id="' . $element['#id'] . '" ';
  $checkbox .= 'value="' . $element['#return_value'] . '" ';
  $checkbox .= $element['#value'] ? ' checked="checked" ' : ' ';
  $checkbox .= drupal_attributes($element['#attributes']) . ' />';
  if (!is_null($element['#title'])) {
    $checkbox = '<label class="option" for="' . $element['#id'] . '">' . $checkbox . ' ' . $element['#title'] . '</label>';
  }
  unset($element['#title']);
  return theme('form_element', $element, $checkbox);
}

/**
 * Format a set of checkboxes.
 *
 * @param $element
 *   An associative array containing the properties of the element.
 * @return
 *   A themed HTML string representing the checkbox set.
 *
 * @ingroup themeable
 */
function theme_checkboxes($element) {
  $class = 'form-checkboxes';
  if (isset($element['#attributes']['class'])) {
    $class .= ' ' . $element['#attributes']['class'];
  }
  $element['#children'] = '<div class="' . $class . '">' . (!empty($element['#children']) ? $element['#children'] : '') . '</div>';
  if ($element['#title'] || $element['#description']) {
    unset($element['#id']);
    return theme('form_element', $element, $element['#children']);
  }
  else {
    return $element['#children'];
  }
}
function expand_checkboxes($element) {
  $value = is_array($element['#value']) ? $element['#value'] : array();
  $element['#tree'] = TRUE;
  if (count($element['#options']) > 0) {
    if (!isset($element['#default_value']) || $element['#default_value'] == 0) {
      $element['#default_value'] = array();
    }
    foreach ($element['#options'] as $key => $choice) {
      if (!isset($element[$key])) {
        $element[$key] = array(
          '#type' => 'checkbox',
          '#processed' => TRUE,
          '#title' => $choice,
          '#return_value' => $key,
          '#default_value' => isset($value[$key]),
          '#attributes' => $element['#attributes'],
          '#ahah' => isset($element['#ahah']) ? $element['#ahah'] : NULL,
        );
      }
    }
  }
  return $element;
}

/**
 * Theme a form submit button.
 *
 * @ingroup themeable
 */
function theme_submit($element) {
  return theme('button', $element);
}

/**
 * Theme a form button.
 *
 * @ingroup themeable
 */
function theme_button($element) {

  // Make sure not to overwrite classes.
  if (isset($element['#attributes']['class'])) {
    $element['#attributes']['class'] = 'form-' . $element['#button_type'] . ' ' . $element['#attributes']['class'];
  }
  else {
    $element['#attributes']['class'] = 'form-' . $element['#button_type'];
  }
  return '<input type="submit" ' . (empty($element['#name']) ? '' : 'name="' . $element['#name'] . '" ') . 'id="' . $element['#id'] . '" value="' . check_plain($element['#value']) . '" ' . drupal_attributes($element['#attributes']) . " />\n";
}

/**
 * Theme a form image button.
 *
 * @ingroup themeable
 */
function theme_image_button($element) {

  // Make sure not to overwrite classes.
  if (isset($element['#attributes']['class'])) {
    $element['#attributes']['class'] = 'form-' . $element['#button_type'] . ' ' . $element['#attributes']['class'];
  }
  else {
    $element['#attributes']['class'] = 'form-' . $element['#button_type'];
  }
  return '<input type="image" name="' . $element['#name'] . '" ' . (!empty($element['#value']) ? 'value="' . check_plain($element['#value']) . '" ' : '') . 'id="' . $element['#id'] . '" ' . drupal_attributes($element['#attributes']) . ' src="' . base_path() . $element['#src'] . '" ' . (!empty($element['#title']) ? 'alt="' . check_plain($element['#title']) . '" title="' . check_plain($element['#title']) . '" ' : '') . "/>\n";
}

/**
 * Format a hidden form field.
 *
 * @param $element
 *   An associative array containing the properties of the element.
 *   Properties used:  value, edit
 * @return
 *   A themed HTML string representing the hidden form field.
 *
 * @ingroup themeable
 */
function theme_hidden($element) {
  return '<input type="hidden" name="' . $element['#name'] . '" id="' . $element['#id'] . '" value="' . check_plain($element['#value']) . "\" " . drupal_attributes($element['#attributes']) . " />\n";
}

/**
 * Format a form token.
 *
 * @ingroup themeable
 */
function theme_token($element) {
  return theme('hidden', $element);
}

/**
 * Process function to prepare autocomplete data.
 *
 * @param $element
 *   A textfield or other element with a #autocomplete_path.
 *
 * @return array
 *   The processed form element.
 */
function form_process_autocomplete($element) {
  $element['#autocomplete_input'] = array();
  if ($element['#autocomplete_path'] && menu_valid_path(array(
    'link_path' => $element['#autocomplete_path'],
  ))) {
    $element['#autocomplete_input']['#id'] = $element['#id'] . '-autocomplete';

    // Force autocomplete to use non-clean URLs since this protects against the
    // browser interpreting the path plus search string as an actual file.
    $current_clean_url = isset($GLOBALS['conf']['clean_url']) ? $GLOBALS['conf']['clean_url'] : NULL;
    $GLOBALS['conf']['clean_url'] = 0;
    $element['#autocomplete_input']['#url_value'] = check_url(url($element['#autocomplete_path'], array(
      'absolute' => TRUE,
    )));
    $GLOBALS['conf']['clean_url'] = $current_clean_url;
  }
  return $element;
}

/**
 * Format a textfield.
 *
 * @param $element
 *   An associative array containing the properties of the element.
 *   Properties used:  title, value, description, size, maxlength, required, attributes autocomplete_path
 * @return
 *   A themed HTML string representing the textfield.
 *
 * @ingroup themeable
 */
function theme_textfield($element) {
  $size = empty($element['#size']) ? '' : ' size="' . $element['#size'] . '"';
  $maxlength = empty($element['#maxlength']) ? '' : ' maxlength="' . $element['#maxlength'] . '"';
  $class = array(
    'form-text',
  );
  $extra = '';
  $output = '';
  if ($element['#autocomplete_path'] && !empty($element['#autocomplete_input'])) {
    drupal_add_js('misc/autocomplete.js');
    $class[] = 'form-autocomplete';
    $extra = '<input class="autocomplete" type="hidden" id="' . $element['#autocomplete_input']['#id'] . '" value="' . $element['#autocomplete_input']['#url_value'] . '" disabled="disabled" />';
  }
  _form_set_class($element, $class);
  if (isset($element['#field_prefix'])) {
    $output .= '<span class="field-prefix">' . $element['#field_prefix'] . '</span> ';
  }
  $output .= '<input type="text"' . $maxlength . ' name="' . $element['#name'] . '" id="' . $element['#id'] . '"' . $size . ' value="' . check_plain($element['#value']) . '"' . drupal_attributes($element['#attributes']) . ' />';
  if (isset($element['#field_suffix'])) {
    $output .= ' <span class="field-suffix">' . $element['#field_suffix'] . '</span>';
  }
  return theme('form_element', $element, $output) . $extra;
}

/**
 * Format a form.
 *
 * @param $element
 *   An associative array containing the properties of the element.
 *   Properties used: action, method, attributes, children
 * @return
 *   A themed HTML string representing the form.
 *
 * @ingroup themeable
 */
function theme_form($element) {

  // Anonymous div to satisfy XHTML compliance.
  $action = $element['#action'] ? 'action="' . check_url($element['#action']) . '" ' : '';
  return '<form ' . $action . ' accept-charset="UTF-8" method="' . $element['#method'] . '" id="' . $element['#id'] . '"' . drupal_attributes($element['#attributes']) . ">\n<div>" . $element['#children'] . "\n</div></form>\n";
}

/**
 * Format a textarea.
 *
 * @param $element
 *   An associative array containing the properties of the element.
 *   Properties used: title, value, description, rows, cols, required, attributes
 * @return
 *   A themed HTML string representing the textarea.
 *
 * @ingroup themeable
 */
function theme_textarea($element) {
  $class = array(
    'form-textarea',
  );

  // Add teaser behavior (must come before resizable)
  if (!empty($element['#teaser'])) {
    drupal_add_js('misc/teaser.js');

    // Note: arrays are merged in drupal_get_js().
    drupal_add_js(array(
      'teaserCheckbox' => array(
        $element['#id'] => $element['#teaser_checkbox'],
      ),
    ), 'setting');
    drupal_add_js(array(
      'teaser' => array(
        $element['#id'] => $element['#teaser'],
      ),
    ), 'setting');
    $class[] = 'teaser';
  }

  // Add resizable behavior
  if ($element['#resizable'] !== FALSE) {
    drupal_add_js('misc/textarea.js');
    $class[] = 'resizable';
  }
  _form_set_class($element, $class);
  return theme('form_element', $element, '<textarea cols="' . $element['#cols'] . '" rows="' . $element['#rows'] . '" name="' . $element['#name'] . '" id="' . $element['#id'] . '" ' . drupal_attributes($element['#attributes']) . '>' . check_plain($element['#value']) . '</textarea>');
}

/**
 * Format HTML markup for use in forms.
 *
 * This is used in more advanced forms, such as theme selection and filter format.
 *
 * @param $element
 *   An associative array containing the properties of the element.
 *   Properties used: value, children.
 * @return
 *   A themed HTML string representing the HTML markup.
 *
 * @ingroup themeable
 */
function theme_markup($element) {
  return (isset($element['#value']) ? $element['#value'] : '') . (isset($element['#children']) ? $element['#children'] : '');
}

/**
 * Format a password field.
 *
 * @param $element
 *   An associative array containing the properties of the element.
 *   Properties used:  title, value, description, size, maxlength, required, attributes
 * @return
 *   A themed HTML string representing the form.
 *
 * @ingroup themeable
 */
function theme_password($element) {
  $size = $element['#size'] ? ' size="' . $element['#size'] . '" ' : '';
  $maxlength = $element['#maxlength'] ? ' maxlength="' . $element['#maxlength'] . '" ' : '';
  _form_set_class($element, array(
    'form-text',
  ));
  $output = '<input type="password" name="' . $element['#name'] . '" id="' . $element['#id'] . '" ' . $maxlength . $size . drupal_attributes($element['#attributes']) . ' />';
  return theme('form_element', $element, $output);
}

/**
 * Expand weight elements into selects.
 */
function process_weight($element) {
  for ($n = -1 * $element['#delta']; $n <= $element['#delta']; $n++) {
    $weights[$n] = $n;
  }
  $element['#options'] = $weights;
  $element['#type'] = 'select';
  $element['#is_weight'] = TRUE;
  $element += _element_info('select');
  return $element;
}

/**
 * Format a file upload field.
 *
 * @param $title
 *   The label for the file upload field.
 * @param $name
 *   The internal name used to refer to the field.
 * @param $size
 *   A measure of the visible size of the field (passed directly to HTML).
 * @param $description
 *   Explanatory text to display after the form item.
 * @param $required
 *   Whether the user must upload a file to the field.
 * @return
 *   A themed HTML string representing the field.
 *
 * @ingroup themeable
 *
 * For assistance with handling the uploaded file correctly, see the API
 * provided by file.inc.
 */
function theme_file($element) {
  _form_set_class($element, array(
    'form-file',
  ));
  return theme('form_element', $element, '<input type="file" name="' . $element['#name'] . '"' . ($element['#attributes'] ? ' ' . drupal_attributes($element['#attributes']) : '') . ' id="' . $element['#id'] . '" size="' . $element['#size'] . "\" />\n");
}

/**
 * Return a themed form element.
 *
 * @param element
 *   An associative array containing the properties of the element.
 *   Properties used: title, description, id, required
 * @param $value
 *   The form element's data.
 * @return
 *   A string representing the form element.
 *
 * @ingroup themeable
 */
function theme_form_element($element, $value) {

  // This is also used in the installer, pre-database setup.
  $t = get_t();
  $output = '<div class="form-item"';
  if (!empty($element['#id'])) {
    $output .= ' id="' . $element['#id'] . '-wrapper"';
  }
  $output .= ">\n";
  $required = !empty($element['#required']) ? '<span class="form-required" title="' . $t('This field is required.') . '">*</span>' : '';
  if (!empty($element['#title'])) {
    $title = $element['#title'];
    if (!empty($element['#id'])) {
      $output .= ' <label for="' . $element['#id'] . '">' . $t('!title: !required', array(
        '!title' => filter_xss_admin($title),
        '!required' => $required,
      )) . "</label>\n";
    }
    else {
      $output .= ' <label>' . $t('!title: !required', array(
        '!title' => filter_xss_admin($title),
        '!required' => $required,
      )) . "</label>\n";
    }
  }
  $output .= " {$value}\n";
  if (!empty($element['#description'])) {
    $output .= ' <div class="description">' . $element['#description'] . "</div>\n";
  }
  $output .= "</div>\n";
  return $output;
}

/**
 * Sets a form element's class attribute.
 *
 * Adds 'required' and 'error' classes as needed.
 *
 * @param &$element
 *   The form element.
 * @param $name
 *   Array of new class names to be added.
 */
function _form_set_class(&$element, $class = array()) {
  if ($element['#required']) {
    $class[] = 'required';
  }
  if (form_get_error($element)) {
    $class[] = 'error';
  }
  if (isset($element['#attributes']['class'])) {
    $class[] = $element['#attributes']['class'];
  }
  $element['#attributes']['class'] = implode(' ', $class);
}

/**
 * Prepare an HTML ID attribute string for a form item.
 *
 * Remove invalid characters and guarantee uniqueness.
 *
 * @param $id
 *   The ID to clean.
 * @param $flush
 *   If set to TRUE, the function will flush and reset the static array
 *   which is built to test the uniqueness of element IDs. This is only
 *   used if a form has completed the validation process. This parameter
 *   should never be set to TRUE if this function is being called to
 *   assign an ID to the #ID element.
 * @return
 *   The cleaned ID.
 */
function form_clean_id($id = NULL, $flush = FALSE) {
  static $seen_ids = array();
  if ($flush) {
    $seen_ids = array();
    return;
  }
  $id = str_replace(array(
    '][',
    '_',
    ' ',
  ), '-', $id);

  // Ensure IDs are unique. The first occurrence is held but left alone.
  // Subsequent occurrences get a number appended to them. This incrementing
  // will almost certainly break code that relies on explicit HTML IDs in
  // forms that appear more than once on the page, but the alternative is
  // outputting duplicate IDs, which would break JS code and XHTML
  // validity anyways. For now, it's an acceptable stopgap solution.
  if (isset($seen_ids[$id])) {
    $id = $id . '-' . $seen_ids[$id]++;
  }
  else {
    $seen_ids[$id] = 1;
  }
  return $id;
}

/**
 * @} End of "defgroup form_api".
 */

/**
 * @defgroup batch Batch operations
 * @{
 * Functions allowing forms processing to be spread out over several page
 * requests, thus ensuring that the processing does not get interrupted
 * because of a PHP timeout, while allowing the user to receive feedback
 * on the progress of the ongoing operations.
 *
 * The API is primarily designed to integrate nicely with the Form API
 * workflow, but can also be used by non-FAPI scripts (like update.php)
 * or even simple page callbacks (which should probably be used sparingly).
 *
 * Example:
 * @code
 * $batch = array(
 *   'title' => t('Exporting'),
 *   'operations' => array(
 *     array('my_function_1', array($account->uid, 'story')),
 *     array('my_function_2', array()),
 *   ),
 *   'finished' => 'my_finished_callback',
 *   'file' => 'path_to_file_containing_myfunctions',
 * );
 * batch_set($batch);
 * // Only needed if not inside a form _submit handler.
 * // Setting redirect in batch_process.
 * batch_process('node/1');
 * @endcode
 *
 * Note: if the batch 'title', 'init_message', 'progress_message', or
 * 'error_message' could contain any user input, it is the responsibility of
 * the code calling batch_set() to sanitize them first with a function like
 * check_plain() or filter_xss().
 *
 * Sample batch operations:
 * @code
 * // Simple and artificial: load a node of a given type for a given user
 * function my_function_1($uid, $type, &$context) {
 *   // The $context array gathers batch context information about the execution (read),
 *   // as well as 'return values' for the current operation (write)
 *   // The following keys are provided :
 *   // 'results' (read / write): The array of results gathered so far by
 *   //   the batch processing, for the current operation to append its own.
 *   // 'message' (write): A text message displayed in the progress page.
 *   // The following keys allow for multi-step operations :
 *   // 'sandbox' (read / write): An array that can be freely used to
 *   //   store persistent data between iterations. It is recommended to
 *   //   use this instead of $_SESSION, which is unsafe if the user
 *   //   continues browsing in a separate window while the batch is processing.
 *   // 'finished' (write): A float number between 0 and 1 informing
 *   //   the processing engine of the completion level for the operation.
 *   //   1 (or no value explicitly set) means the operation is finished
 *   //   and the batch processing can continue to the next operation.
 *
 *   $node = node_load(array('uid' => $uid, 'type' => $type));
 *   $context['results'][] = $node->nid .' : '. $node->title;
 *   $context['message'] = $node->title;
 * }
 *
 * // More advanced example: multi-step operation - load all nodes, five by five
 * function my_function_2(&$context) {
 *   if (empty($context['sandbox'])) {
 *     $context['sandbox']['progress'] = 0;
 *     $context['sandbox']['current_node'] = 0;
 *     $context['sandbox']['max'] = db_result(db_query('SELECT COUNT(DISTINCT nid) FROM {node}'));
 *   }
 *   $limit = 5;
 *   $result = db_query_range("SELECT nid FROM {node} WHERE nid > %d ORDER BY nid ASC", $context['sandbox']['current_node'], 0, $limit);
 *   while ($row = db_fetch_array($result)) {
 *     $node = node_load($row['nid'], NULL, TRUE);
 *     $context['results'][] = $node->nid .' : '. $node->title;
 *     $context['sandbox']['progress']++;
 *     $context['sandbox']['current_node'] = $node->nid;
 *     $context['message'] = $node->title;
 *   }
 *   if ($context['sandbox']['progress'] != $context['sandbox']['max']) {
 *     $context['finished'] = $context['sandbox']['progress'] / $context['sandbox']['max'];
 *   }
 * }
 * @endcode
 *
 * Sample 'finished' callback:
 * @code
 * function batch_test_finished($success, $results, $operations) {
 *   if ($success) {
 *     $message = format_plural(count($results), 'One post processed.', '@count posts processed.');
 *   }
 *   else {
 *     $message = t('Finished with an error.');
 *   }
 *   drupal_set_message($message);
 *   // Providing data for the redirected page is done through $_SESSION.
 *   foreach ($results as $result) {
 *     $items[] = t('Loaded node %title.', array('%title' => $result));
 *   }
 *   $_SESSION['my_batch_results'] = $items;
 * }
 * @endcode
 */

/**
 * Opens a new batch.
 *
 * @param $batch
 *   An array defining the batch. The following keys can be used -- only
 *   'operations' is required, and batch_init() provides default values for
 *   the messages.
 *   - 'operations': Array of function calls to be performed.
 *     Example:
 *     @code
 *     array(
 *       array('my_function_1', array($arg1)),
 *       array('my_function_2', array($arg2_1, $arg2_2)),
 *     )
 *     @endcode
 *   - 'title': Title for the progress page. Only safe strings should be passed.
 *     Defaults to t('Processing').
 *   - 'init_message': Message displayed while the processing is initialized.
 *     Defaults to t('Initializing.').
 *   - 'progress_message': Message displayed while processing the batch.
 *     Available placeholders are @current, @remaining, @total, and
 *     @percentage. Defaults to t('Completed @current of @total.').
 *   - 'error_message': Message displayed if an error occurred while processing
 *     the batch. Defaults to t('An error has occurred.').
 *   - 'finished': Name of a function to be executed after the batch has
 *     completed. This should be used to perform any result massaging that
 *     may be needed, and possibly save data in $_SESSION for display after
 *     final page redirection.
 *   - 'file': Path to the file containing the definitions of the
 *     'operations' and 'finished' functions, for instance if they don't
 *     reside in the main .module file. The path should be relative to
 *     base_path(), and thus should be built using drupal_get_path().
 *
 * Operations are added as new batch sets. Batch sets are used to ensure
 * clean code independence, ensuring that several batches submitted by
 * different parts of the code (core / contrib modules) can be processed
 * correctly while not interfering or having to cope with each other. Each
 * batch set gets to specify its own UI messages, operates on its own set
 * of operations and results, and triggers its own 'finished' callback.
 * Batch sets are processed sequentially, with the progress bar starting
 * fresh for every new set.
 */
function batch_set($batch_definition) {
  if ($batch_definition) {
    $batch =& batch_get();

    // Initialize the batch
    if (empty($batch)) {
      $batch = array(
        'sets' => array(),
      );
    }
    $init = array(
      'sandbox' => array(),
      'results' => array(),
      'success' => FALSE,
    );

    // Use get_t() to allow batches at install time.
    $t = get_t();
    $defaults = array(
      'title' => $t('Processing'),
      'init_message' => $t('Initializing.'),
      'progress_message' => $t('Remaining @remaining of @total.'),
      'error_message' => $t('An error has occurred.'),
    );
    $batch_set = $init + $batch_definition + $defaults;

    // Tweak init_message to avoid the bottom of the page flickering down after init phase.
    $batch_set['init_message'] .= '<br/>&nbsp;';
    $batch_set['total'] = count($batch_set['operations']);

    // If the batch is being processed (meaning we are executing a stored submit handler),
    // insert the new set after the current one.
    if (isset($batch['current_set'])) {

      // array_insert does not exist...
      $slice1 = array_slice($batch['sets'], 0, $batch['current_set'] + 1);
      $slice2 = array_slice($batch['sets'], $batch['current_set'] + 1);
      $batch['sets'] = array_merge($slice1, array(
        $batch_set,
      ), $slice2);
    }
    else {
      $batch['sets'][] = $batch_set;
    }
  }
}

/**
 * Processes the batch.
 *
 * Unless the batch has been marked with 'progressive' = FALSE, the function
 * issues a drupal_goto and thus ends page execution.
 *
 * This function is not needed in form submit handlers; Form API takes care
 * of batches that were set during form submission.
 *
 * @param $redirect
 *   (optional) Path to redirect to when the batch has finished processing.
 * @param $url
 *   (optional - should only be used for separate scripts like update.php)
 *   URL of the batch processing page.
 */
function batch_process($redirect = NULL, $url = NULL) {
  $batch =& batch_get();
  if (isset($batch)) {

    // Add process information
    $url = isset($url) ? $url : 'batch';
    $process_info = array(
      'current_set' => 0,
      'progressive' => TRUE,
      'url' => isset($url) ? $url : 'batch',
      'source_page' => $_GET['q'],
      'redirect' => $redirect,
    );
    $batch += $process_info;
    if ($batch['progressive']) {

      // Clear the way for the drupal_goto redirection to the batch processing
      // page, by saving and unsetting the 'destination' if any, on both places
      // drupal_goto looks for it.
      if (isset($_REQUEST['destination'])) {
        $batch['destination'] = $_REQUEST['destination'];
        unset($_REQUEST['destination']);
      }
      elseif (isset($_REQUEST['edit']['destination'])) {
        $batch['destination'] = $_REQUEST['edit']['destination'];
        unset($_REQUEST['edit']['destination']);
      }

      // Initiate db storage in order to get a batch id. We have to provide
      // at least an empty string for the (not null) 'token' column.
      db_query("INSERT INTO {batch} (token, timestamp) VALUES ('', %d)", time());
      $batch['id'] = db_last_insert_id('batch', 'bid');

      // Now that we have a batch id, we can generate the redirection link in
      // the generic error message.
      $t = get_t();
      $batch['error_message'] = $t('Please continue to <a href="@error_url">the error page</a>', array(
        '@error_url' => url($url, array(
          'query' => array(
            'id' => $batch['id'],
            'op' => 'finished',
          ),
        )),
      ));

      // Actually store the batch data and the token generated form the batch id.
      db_query("UPDATE {batch} SET token = '%s', batch = '%s' WHERE bid = %d", drupal_get_token($batch['id']), serialize($batch), $batch['id']);
      drupal_goto($batch['url'], 'op=start&id=' . $batch['id']);
    }
    else {

      // Non-progressive execution: bypass the whole progressbar workflow
      // and execute the batch in one pass.
      require_once './includes/batch.inc';
      _batch_process();
    }
  }
}

/**
 * Retrieves the current batch.
 */
function &batch_get() {
  static $batch = array();
  return $batch;
}

/**
 * @} End of "defgroup batch".
 */

Functions

Namesort descending Description
batch_get Retrieves the current batch.
batch_process Processes the batch.
batch_set Opens a new batch.
date_validate Validates the date type to stop dates like February 30, 2006.
drupal_execute Retrieves, populates, and processes a form.
drupal_get_form Retrieves a form from a constructor function, or from the cache if the form was built in a previous page-load. The form is then passed on for processing, after and rendered for display if necessary.
drupal_prepare_form Prepares a structured form array by adding required elements, executing any hook_form_alter functions, and optionally inserting a validation token to prevent tampering.
drupal_process_form This function is the heart of form API. The form gets built, validated and in appropriate cases, submitted.
drupal_rebuild_form Retrieves a form, caches it and processes it with an empty $_POST.
drupal_redirect_form Redirect the user to a URL after a form has been processed.
drupal_render_form Renders a structured form array into themed HTML.
drupal_retrieve_form Retrieves the structured array that defines a given form.
drupal_validate_form Validates user-submitted form data from the $form_state using the validate functions defined in a structured form array.
expand_checkboxes
expand_date Roll out a single date element.
expand_password_confirm Expand a password_confirm field into two text boxes.
expand_radios Roll out a single radios element to a list of radios, using the options array as index.
form_builder Walk through the structured form array, adding any required properties to each element and mapping the incoming $_POST data to the proper elements.
form_build_id_map Maintain a map of immutable form_build_ids to cloned form.
form_clean_id Prepare an HTML ID attribute string for a form item.
form_error Flag an element as having an error.
form_execute_handlers A helper function used to execute custom validation and submission handlers for a given form. Button-specific handlers are checked first. If none exist, the function falls back to form-level handlers.
form_expand_ahah Add AHAH information about a form element to the page to communicate with javascript. If #ahah[path] is set on an element, this additional javascript is added to the page header to attach the AHAH behaviors. See ahah.js for more information.
form_get_cache Fetch a form from cache.
form_get_error Return the error message filed against the form with the specified name.
form_get_errors Return an associative array of all errors.
form_get_options Traverses a select element's #option array looking for any values that hold the given key. Returns an array of indexes that match.
form_options_flatten
form_process_autocomplete Process function to prepare autocomplete data.
form_select_options
form_set_cache Store a form in the cache.
form_set_error File an error against a form element.
form_set_value Change submitted form values during the form processing cycle.
form_type_checkboxes_value Helper function to determine the value for a checkboxes form element.
form_type_checkbox_value Helper function to determine the value for a checkbox form element.
form_type_image_button_value Helper function to determine the value for an image button form element.
form_type_password_confirm_value Helper function to determine the value for a password_confirm form element.
form_type_select_value Helper function to determine the value for a select form element.
form_type_textfield_value Helper function to determine the value for a textfield form element.
form_type_token_value Helper function to determine the value for form's token value.
map_month Helper function for usage with drupal_map_assoc to display month names.
password_confirm_validate Validate password_confirm element.
process_weight Expand weight elements into selects.
theme_button Theme a form button.
theme_checkbox Format a checkbox.
theme_checkboxes Format a set of checkboxes.
theme_date Format a date selection element.
theme_fieldset Format a group of form items.
theme_file Format a file upload field.
theme_form Format a form.
theme_form_element Return a themed form element.
theme_hidden Format a hidden form field.
theme_image_button Theme a form image button.
theme_item Format a form item.
theme_markup Format HTML markup for use in forms.
theme_password Format a password field.
theme_password_confirm Format a password_confirm item.
theme_radio Format a radio button.
theme_radios Format a set of radio buttons.
theme_select Format a dropdown menu or scrolling selection box.
theme_submit Theme a form submit button.
theme_textarea Format a textarea.
theme_textfield Format a textfield.
theme_token Format a form token.
weight_value If no default value is set for weight select boxes, use 0.
_element_info Retrieve the default properties for the defined element type.
_form_builder_handle_input_element Populate the #value and #name properties of input elements so they can be processed and rendered. Also, execute any #process handlers attached to a specific element.
_form_builder_ie_cleanup In IE, if only one submit button is present, AND the enter key is used to submit the form, no form value is sent for it and our normal button detection code will never detect a match. We call this function after all other button-detection is complete…
_form_button_was_clicked Helper function to handle the sometimes-convoluted logic of button click detection.
_form_set_class Sets a form element's class attribute.
_form_set_value Helper function for form_set_value().
_form_validate Performs validation on form elements. First ensures required fields are completed, #maxlength is not exceeded, and selected options were in the list of options given to the user. Then calls user-defined validators.